1. Field of The Invention
The invention relates to the field of separating devices for separating flat parcels, such as letters, documents and the like, from a stack, and in particular to an apparatus using a drawing element that travels in a conveying direction and acts by means of friction on a respective parcel to be drawn off.
2. Background Information
Separation methods and devices are known from, for example, European Patent EP 0,142,538. One known problem associated with separation methods and devices is the so-called double-drawing error. This error occurs when in addition to a desired first parcel to be drawn off of a stack, a further second parcel is drawn off. This problem may be due to the frictional force between the first parcel in the stack and the second parcel being too great, or because the second parcel protrudes and is drawn off too early due to an insufficiently uniform alignment of the front edges of the parcels.
The above-described problem is to a degree a function of parameters such as the parcel features, i.e., particularly weight, thickness, roughness and moisture content of the parcel material, as well as environmental conditions, in particular the amount of moisture in the ambient air.